2,3 Substituted, 5,6 or 6,7 ethylene or methylene dioxy quinoxalines

ABSTRACT

A photographic light-sensitive material for the silver bleaching process which comprises on a support in at least one layer a quinoxaline of formula   WHEREIN A1 and A2 are each an alkyl-, aralkyl-, aryl, or heterocyclic group and n is 1 or 2, whereby the oxygencontaining ring is connected with the quinoxaline group in the 5,6- or 6,7position as a colour bleaching catalyst as well as quinoxalines of the formula given above are disclosed.

United States Patent 1191- Schlunke et al.

1451 May 20, 1975 t 1 2,3 SUBSTITUTED, 5,6 OR 6,7 ETHYLENE OR METHYLENE DIOXY QUINOXALINES [75] Inventors: Hans-Peter Schlunke, Marly-le-Petit;

Christian Egli, Magden, both of Switzerland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed: May 21, 1973 [21] Appl. No.: 361,913

Related US. Application Data [62] Division of Ser. No. 176,689, Aug. 31, 1971, Pat. No.

[30] Foreign Application Priority Data OTHER PUBLICATIONS Krajewski, et al., J. Agr. Food Chem. 1971, pp. 298-301.

Mariconi et al., J. Org. Chem., 30 1542-1547 (1955).

Primary Examine rD0nald G. Daus Assistant Examiner-David E. Wheeler Attorney, Agent, or FirmJoseph G. Kolodny; Edward McC. Roberts; Prabodh I. Almaula [57] ABSTRACT A photographic light-sensitive material for the silver bleaching process which comprises on a support in at least one layer a quinoxaline of formula N\ l (cg fl I (1') wherein A and A are each an alkyl-, aralkyl-, aryl, or heterocyclic group and n is l or 2, whereby the 0xygencontaining ring is connected with the quinoxaline group in the 5,6- or 6,7-position as a colour bleaching catalyst as well as quinoxalines of the formula given above are disclosed.

I 4 Claims, No Drawings 2,3 SUBSTITUTED, 5,6 OR 6,7 ETHYLENE OR METHYLENE DIOXY QUINOXALINES I This is a divisional of application US. Pat. Ser. No. 176,689, filed Aug. 31, 1971, US. Pat. No. 3,767,402.

This invention relates to photographic material which contains quinoxalines as colour bleaching catalysts.

According to the present invention these is provided a photographic eight-sensitive material for the silver bleaching process which comprises on a support in at least one layer a quinoxaline of formula A /o t 1 (crr g fl I (1) wherein A and A each represent an alkyl group with at most of 5 carbon atoms, an at most bicyclic aralkyl group with l to 5 carbon atoms in the alkyl portion, an at most bicyclic aryl group or a 5 or 6-membered heterocyclic group having N, O or S as heteroatoms and n represents 1 or 2, whereby the oxygen-containing ring is connected with the quinoxaline group in the 5,6 or 6,7-position, as colour bleaching catalysts. Advantageously quinoxalines of formula are used, wherein A and A each represent an alkyl group with at most 5 carbon atoms or an optionally substituted benzene group and n represents 1 or 2, whereby the rings are interconnected in the indicated manner.

Groups A, and A or A and A, as well as groups A and A of the following formula (3) can be the same or different. Alkyl groups with l to 5, preferably 1 to 3 carbon atoms which can be used are e.g. amyl, n-sec. ,or tert. butyl, n or isopropyl, ethyl or in particular methyl groups. As at most bicylic aralkyl groups are mentioned e.g. the naphthenyl or benzyl group. The at most bicyclic aryl groups are naphthalene, diphenyl or benzene groups, having optionally further substituents such as e.g. lower alkyl, lower alkoxy, hydroxy, substituted amines, amine or halogen. Particularly lower alkyl groups can be used as substituents for the amine. Heterocyclic 5 or 6-membered groups which can be used are e.g. pyridyl, furyl or thienyl groups.

Depending on whether n is l to 2 the compounds of formula l are dioxolo or dioxano quinoxalines.

Of particular interest are quinoxalines of formula wherein A and A each represent a methyl or phenyl group and n is l or 2, whereby the rings are interconnected in the indicated manner.

Among these quinoxalines those of formula wherein A is a methyl or phenyl group and n is l or 2, whereby the rings are interconnected in the indicated manner, are particularly suitable.

The quinoxalines of formula (1) can be used as colour bleaching catalysts in a processing bath, preferably in a colour bleaching bath and/or in a layer of the photographic material.

The reduction products of the quinoxalines of formula (1) can also be used for so-called bleach development, by themselves acting as hydrogen developers in an acid medium.

Such processes are known e.g. from French Pat. No. 1,565,800.

The quinoxalines of formula (1) can be used either alone or in the presence of other conventional colour bleaching catalysts. It is also possible to use various quinoxalines of formula (1) simultaneously in the colour bleaching bath. Finally the quinoxalines of formula (1) can also be used together with other bleachingpromoting measures, e.g. together with an irradiation or bubbling with a gas of the colour bleaching bath or" corporated into a coating free from bleachable image dye. The multi-layer material can therefore have for example an additional gelatin layer containing only the catalyst located directly on the emulsion carrier or between two colour layers. In the latter case the catalystcontaining layer also acts as a separating layer. In addition, the catalyst can also be incorporated into colloidal silver or layers containing filter or antihalo dye or covering coatings. These filter layers as well as the coatings with the image dyes advantageously contain gelatin as the layers colloid.

However, the quinoxalines of formula l can also be incorporated directly into a layer containing image dye.

Furthermore, the multi-layer material can have the conventional composition. Colour-photographic images can be produced in per se known manner with the photographic materials .of the indicated composition.

The colour bleaching catalysts of formula 1) can, as already indicated, e.g. be added to the colour bleaching bath where they then directly exert their action. They can also be added to a previous treatment bath, e.g. the developer, a hardening bath, a stop bath or a special bath preceeding the silver bleaching bath. In this way a certain portion of the. catalyst quantity introduced is absorbed and retained by. the photographic coating materialuntil it can act in the colour bleaching bath. De

tion of the corresponding aromatic l,2-diamine with a l,2-dicarbonyl compound. Instead of diamine it is possible to use the corresponding more stable nitroaniline or the corresponding o-dinitro compound, which can be reduced to the desired diamine and then without intermediate separation reacted to give quinoxaline. The corresponding benzofuroxans or their reduction products (benzofurazans can also be reduced pending on the particular use the quantity of catalyst used can vary within wide limits. Generally it suffices for a strong action to add 0.001 to 0.1g of catalyst to 1 litre of a colour bleaching bath of normal composition containing a silver complex constituent such as e. g. alkali metal bromide or iodide or thiourea and optionally an anti-oxidising agent such as e.g. sodium hypophosphite and forgiving the necessary pH-value a strong organic or inorganic acid such as e.g. benzenesulphonic acid, hydrochloric acid, sulphuric acid, phosphoric acid or sodium bisulphate.

Further objects of the invention are therefore a photographic, light-sensitive material for the silver dyebleach process containing on a carrier in at least one layer as a colour bleaching catalyst a quinoxaline of formula( 1) and photographic processing baths, particularly colour bleaching baths, characterised in that as the colour bleaching catalyst they contain at least a quinox aline of formula.( 1).

A further object of the invention is a process for producing colour photographic images according to the silver dye-bleach process on materials containing on a substrate at least one silver halide emulsion layer with a bleachable imagedye by exposure, developing the silver image and colour bleaching, characterised in that the colour bleaching is performed in the presence of at least one quinoxaline of formula (1) as the colour bleaching catalyst.

The hitherto known compounds used in the silver bleaching process as colour bleaching catalysts have a widely different action on azo dyes of differing constitution. Whereas they can be very effective with one class of azo dyes, they may have only a very slight bleaching-promoting action with another class. Thus, there is a need for compounds which alone or in combination bringabout a uniform bleaching of all three layer dyes of a multi-layer material.

It has been found that quinoxalines of formula (1) are admirably suited for this purpose. They are characterised by a very favourable position of their redox potentials and good solubility in the colour bleaching bath in the requisite concentrations. Particularly if the groups A and A of formula (1) each represent a methyl group the quinoxalines according to the invention of formula (1) have a good activity and lead to a to l,2-diamines via intermediate stages (F. B. Mallory S. P. Varimbi, J. Org. Chem., 28, l65ff, 1963) and condensed to quinoxalines.

Instead of the l,2-dicarbonyl compound it is also possible to react an a-substituted halogeno ketone of formula C(X)CO, wherein X is a nucleo'philic group, e.g. -I, -Br, Cl, or -OH with the o-diamine to give the corresponding l,2-dihydroquinoxaline (J. Figueras, J. Org. Chem., 3 l 803ff, 1966), which is then oxidised in situ to quinoxaline.

The quinoxalines are obtained in better yield and greater purity if the condensation is performed under nitrogen.

a-Oximinoketones can also be reacted with l,2- diamines to give quinoxalines (cf. J. C. E. Simpson, loc. cit.).

As starting materials for one of the indicated syntheses can e.g. be used the compounds given in the following table. l,2-Dicarbonyl compounds, a-halogenoketones, a-Oximinoketones V diacetyl 3-bromobutanone-2 3-chlorobutanone 3-iodbutanone 3-oximinobutanone-2 hexandione-3 ,4

benzil benzoin bromodesoxybenzoin l-phenylpropandionel ,2

l-phenyl-2-oximinopropanone-1 bromopropiophenone chloropropiophenone 2'-hydroxypropiophenone di-(a-naphthyU-diketone di-(B-naphthyU-diketone a-pyridil 'y-pyridil di-(2-thienyl)-diketone di-( 2-furyl )-diketone o-dinitrobenzenes, o-nitroanilines, l,2-diamines [4,5-d]-dioxolo-l ,Z-dinitrobenzene [4,5-d]-dioxolol -amino-2-nitrobenzene [4,5-d -dioxolol ,2-diaminobenzene [3,4-d1-dioxolo-l ,2-dinitrobenzene [3 ,4-d]-dioxolol -amino-2-nitrobenzene [3 ,4-d -dioxolol -nitro-2-aminobenzene [3 ,4-d -dioxolol ,2-diaminobenzene [4,5-b]-dioxanol ,Z-dinitrobenzene [4,5-b -dioxanol -amino-2-nitrobenzene [4,5-b]-dioxano-l ,2-diaminobenzene [3,4-b]-dioxanol ,2-dinitrobenzene [3 ,4-bl-dioxano- 1 -amino-2-nitrobenzene [3 ,4-b]-dioxanol -nitro-2-aminobenzene [3 ,4-b]-dioxano-l ,2-diaminobenzene benzofuroxans, benzofurazans [5,6-d]-dioxolobenzofuroxan [5,6-d]-dioxolobenzofurazan [4,5 6,7 )-d i-dioxolobenzofuroxan [4,5-d]-dioxolobenzofurazan [5 ,6-bl-dioxanobenzofuroxan [5 ,6-b l-dioxanobenzofurazan [4,5 6 ,7 )-b]-dioxanobenzofuroxan [4,5-b]-dioxanobenzofurazan The quinoxalines of formula (1) are new and can serve as intermediates e.g. in the preparation of pharmaceutically active compounds.

The percentages in the following preparation instructions and examples are percentages by weight.

Preparation Instructions General instructions An appropriate o-dinitro derivative is dissolved in a suitable solvent e.g. methanol, ethanol, glacial acetic acid or dimethyl formamide or also only suspended with l to 10 percent by weight of hydrogenation catalyst e.g. a 10 percent palladium-carbon catalyst and bydrogenated under normal pressure, optionally with initial heating. When the reaction is terminated the catalyst is filtered off under N and the filtrate under N is mixed with an at least equimolar quantity of distilled or recrystallised diketone or a solution of the diketone in a suitable solvent, whereby in most cases a colour deepening occurs and the temperature rises. Subsequently the mixture is refluxed until the end of the reaction and the desired substance is isolated after cooling. The product can be purified by recrystallising from a suitable solvent by distillation or if necessary by chromatography or sublimation. Instead of the dinitro deriva tive it is possible in some cases to use the corresponding o-nitroamino compound.

If the ao-diamino compound is single and obtainable 'fficient purity it can be reacted directly or in the forrn aof its salt (hydrochloride, hydrosulphate, hydroperchlorate, etc.) with the corresponding diketone in a suitable solvent under nitrogen. When using a salt it is recommended that an equivalent quantity of sodium or potassium acetate be added to saturate the liberated acid.

For the synthesis of the 2,3-asymetrical compounds filtered off under nitrogen and the filtrate is mixed with 8.6g (IOOmmol) of diacetyl under N The reaction conform with the structure.

B [6,7-d]-dioxolo-2-methyl-3-phenylquinoxaline 3l.5g (l49mmol) of [4,5-d]-dioxolo-l,2- dinitrobenzene are hydrogenated as described in Example A; I-l consumption 21 litres 100 percent of theory. The filtrate'is mixed with 15g of crystallised sodium acetate and 33.25g of freshly distilled bromopropiophenone' and refluxed for 3 hours. The hot solution is mixed with a freshly preparedsolution of 36.5 g of 95 percent sodium-m-nitrobenzenesulphonate and 66g (1.45mol) of sodium hydroxide in 287ml of H 0 and 45ml of ethanol and refluxed for 2 hours. After cooling overnight 300ml ofwater are added and the solution distilled to 500ml. The residue from which al- I ready part of the desired product is precipitated is continuously extracted for 12 hours with 500ml of ethyl acetate.

After treating the organic phase with animal charcoal and filtering, the solvent is removed under reduced the a-diketone is replaced by oz-bromopropiophenone. I

The thus formed 1,2-dihydroquinoxaline is then oxidised with m-nitrobenzenesulphonic acid Na salt in the presence of an aqueous sodium hydroxide solution to give quinoxaline.

The redox potentials are determined in the usual manner by means of polarography. The solvent used is in all cases a mixture of dimethylformamide-2N sulphuric acid in a ratio of 1:1. The potential is measured relative to an Ag/AgCl electrode of known potential and then converted to the potential relative to a normal hydrogen electrode. Whereas in certain cases two single electron transitions, characterised by that two polarographic waves are observed in other cases only one polarographic wave is observed, corresponding to the average redox potential.

The melting points and analysis results of the quinoxalines of formula (1) are given in the table.

A [6,7-d]-dioxolo-2,3-dimethylquinoxaline 20g (94.5mmol) of [4,5-d1-dioxolo-l ,2- dinitrobenzene are dissolved in 200ml of methanol and after adding lg of 10 percent palladium/animal charcoal hydrogenated under normal pressure, whereby the internal temperature rises to 60C; hydrogen consumption 14.1 litres 100 percent of theory. The catalyst is pressure. The'residue is dissolved in a minimum of ethanol, again treated with animal charcoal and the filtrate agitated in 500ml of hot water. After slowly cooling to 0C., 8.7g 2 2,percent of theory) of compound B are finally obtained. The thin-layer chromatogram in toluenezacetone 9:1 reveals in addition to the main quantity four slight impurities. The IR and NMR spectra show the characteristic strips for the required structure.

C [5,6-d]-dioxol0-2,3-dimethylquinoxaline l. [4,5-d]-dioxoloacetanilide 51.4g (308mmol) of [4,5-d]-dioxolonitrobenzene are dissolved in 500ml of ethanol and hydrogenated in the presence of 1.5g of 10. percent palladium/carbon under normal pressure at room temperature. After filtering off the catalyst and evaporating the solvent there remain 41.1 g (=95 percent of theory) of the amino compound as abrown oil which in the thin-layer chromatogram with toluenezacetone 9:1 as the solvent system reveals in addition to the main zone two small impurities. This oil is mixed with 44ml of glacial acetic acid and 35ml of acetic anhydride andafter adding 0.55g of zinc powder is refluxed for 1 hour. The still hot solution is poured onto 200ml. of an ice-water mixture. The resulting crystals are filtered off and dried at 60C in vacuo. Yield 47.8 percent of theory (based on the nitro compound) of m.p. l34.lC. The thin-layer chromatogram in trichloromethane: methanol 9:1 as the solvent system reveals a main spot, whilst the IR and NMR spectra show the strips characteristic of the structure. I

'2. [4,5-d] dioxolo-2,3-dinitroacetanilide 47.8g (266mmol) of [4,5-d]-dioxoloacetanilide are added portion wise accompanied by vigorous stirring at 5l0C. to a mixture of concentrated I-INO (d=l.4) and 166ml of fuming'I-INO (d=l.54). On termination of the additionthe reaction mixture is stirred for a furthin-layer chromatogram in toluene:acetone 6:4 reveals in addition to the main zone two negligible impurities. The IR and NMR spectra conform with the structure. Y

3. [4,5-d]-dioxolo-2,3dinitroaniline 9.6g (35mmol) of [4,5-d]-dioxoIo-2,3- dinitroacetanilide are refluxed for 3 hours in 40ml of ethanol and 4g of 37 percent hydrochloric acid. After cooling to C. 7.1g (=90 percent of theory) of the amine found to be thin-layer chromatographically (solvent system toluene:acetone 7:3) uniform. The IR and NMR spectra show the absorptions to be expected from the structure.

4; [3,4-d]-dioxo1o-1 ,2-dinitrobenzene 7.1 g (31mmol) of [4,5d]dioxolo-2,3-dinitroani1ine suspended in 215ml of glacial acetic acid are diazotised with 7.4g (l07mmol) of sodium nitrite in 70ml of 96 percent sulphuric acid at C. After stirring for 2 hours at room temperature the reaction mixture is poured into 142ml of ethanol. After adding 0.45g of copper powder stirring takes place at room temperature with the end of gas evolution (3 hours).'The reaction mixture is poured onto ice-water. On leaving to stand almost colourless needles are precipitated, which are dissolved in a minimum of methanol and treated with activated charcoal. After adding water 4.7g (74 percent of theory of slightly yellowish and fine needles are obtained. The thin-layer chromatogram in toluene- :acetone 7:3 reveals in addition to the main spot one slight impurity. The IR and NMR spectra conform with the structure. t

5. [5,6-d]-dioxolo-2,3-dimethylquinoxaline genated in 50ml of ethanol as the solvent. After adding 1.3g l5mmol) of diacetyl the reaction mixture is refluxed for 1 hour. The thus obtained residue is taken up in 30ml of methanol, again treated with animal charcoal and finally cooled to 50C. Thereby 1 g (=33 percent of theory) of almost colourless crystals are obtained,'which in the thin-layer chromatogram with toluenezacetone 9:1 as the solvent system reveal in addition to the main spot one slight impurity. The IR and NMR spectra reveal the characteristic strips expected fromthe structure.

D. [5,6-bl dioxano-2,3-dimethy1quinoxa1ine 9.0g (40mmol) of [3,4-b]-dioxano-1,2- dinitrobenzene, dissolved in 250ml of ethanol are hydrogenated in the presence of Raney nickel (activity .W5) and 0.5g of 10 percent palladium/carbon at room temperature and normal pressure; H consumption 5300m1 90 percent of theory. After filtering off the catalyst and adding 3.5ml (40mmol) of diacetyl the solution isrefluxed for 1 hour and evaporated to about 50ml under reduced pressure. The residue is treated with activated charcoal and the filtrate cooled to l0C, whereby 2.9g 33 percent of theory of compound D are obtained. The thin-layer chromatogram in toluene:acetone 8:2 as the solvent system reveals no. impurities. The IR and NMR spectra conform with the structure.

E. l6,7-b]dioxano-Z, 3-diphenylquinoxaline 9.0g (40mmol) of [4,5-b]-dioxano-1,2- dinitrobenzene, dissolved in 250ml of ethyl acetate are hydrogenated as described under D. The filtrate is mixed with 8.4g (40mmol) of benzil and refluxed for 1 5 hour. After cooling tovroom temperature the solvent is structure.

The other compounds shown in Table 1 werepre* 3.1g (15 mrnol) 0f [3, I- l pared analogously to one of the hereinbefore described dinitrobenzene are, as described in Example A, hydroi t i I I I Table I i In formula (1) l 4 Analysis Melting q, Connection 0 C H N Compound A A n point C point calc. found calc. found 02110. found A on e11 1 6,7 213,5 65.34 65.47 4.98 I 5.05 15.85 15.95

B cH c 11 1 6,7 125,2 72,72 72,61 4,58 4.51 1 10,60 10,48

D CH 01 2 5,6 141,5 66,65 66,58 5. 59 5. 54 12,96 12,84

E C6115 C6115 2 6,7 225.,0 77.63 77,53 4,74 4, 77 3 4 Table I- ficontinuation Q In formula (1) Melfing Analysis c, cs d Connectior point C C H I N Compound A A I] point calc. found calc. found calc. found G H H l 5. 136.9 77.29 77.37 4.32 4.51 .5 .30

H CH CH 2 6,7 189,9 66,65 66.36 5.59 5. 3 12.96 13.1

I CH (3 H 6,7 105.6 73.37 73.52 5. 7 4.98 10. 7 '9.90

J C H C H 2 5,6 192. 77. 3 77.79 4.74 4.72 8.23 8,

Table I lcontinuation Z In formula (1) 7 Analysis Melting Connect- 0 73 C 75 H fill point C. Compound A A n ion cale. found calc. found calc. iound point K I Q 1 6,7' 205,1 69.50 69.24 3.68 5.72 17.07 16.71

5 3 M N-@- N@ 1 6,7 276,0 72,80 75,25 5,86 6,03 15.58 15.55

17 H C0-@ H CO-@ '1 6.7 170.2 71,49 71,65 4.70 4.75 7.25 6.94

EXAMPLE 1 50 and l.lml of water. After drying the thus obtained lam- OCH HOS SOH 3 SOH SO H inar bond a step wedge is copied thereon (5O lux, 3 sec.) and then the copy is developed as follows:

1. develop for 6 minutes in a bath containing per litre 50g of anhydrous sodium sulphite, 0.2g of l-phenyl-3-pyrazolidone, 6g of hydroquinone, 35g of anhydrous sodium carbonate, 4g of potassium bromide and 0.3g of benzotriazole;

2. fix for 2 minutes with a solution of 200g of sodium thiosulphate, 10g of sodium sulphite, 20g of so- 11 A 12 dium acetate and 10ml of glacial acetic acid per and a covering layer. All these layers are hardened with litre of water; a halogenotriazine compound such as 2,4-dichloro-6- 3. rinse for 4 minutes; 1 phenylamino-l,3,5-triazino-3'-sulphonic acid.

4. colour bleach for 6 minutes with a solution of 10g This copying material is successively exposed under of potassium iodide in 1 litre of lN-sulphuric acid; a step wedge into the three spectral areas blue (Kodak 5. rinse for 2 minutes; Wratten filter 2B+49), green (Kodak Wratten filter 6. bleach for remaining silver for 2 minutes with a 16+61) and red (Kodak Wratten filter 2X29) and, as bath containing 150ml of 37 percent hydrochloric described in Example 1 developed for 7 minutes and acid, 25g of copper sulphate and 30g of potassium fixed. Subsequently bleaching takes place in a silver bromide per litre, 10 bleaching bath containing per litre 27ml of 96 percent 7. rinse for 2 minutes; sulphuric acid, 10g of potassium iodide and 10ml of a 8. fix for 4 minutes as under 2); 4.10 molar solution of compound A in glacial acetic 9. rinse for 10 minutes. acid. After a brief rinsing the remaining silver is, as de- After drying the clean colourless bleached photoscribed in Example 1 under (6), oxidised, rinsed and graph is obtained with a clearly graduated gradation of fixed as described above. After thorough washing-out the wedge used as the original. and drying a white-bleached neutral wedge is obtained,

EXAMPLE 2 opposite to the original in its gradation.

EXAMPLE 4 If instead of compound G compound E dissolved in dimethyl formamide is used, then proceeding as de- Instead of compound Aas in Example 3,it is possible scribed in Example 1 again a clean positive image of to use compound B or any other quinoxaline indicated the exposed wedge is obtained. If instead of compound in Table I dissolved in a suitable photographically inac- G compound J is used as an acetic solution, then pro- 'tive, water-miscible solvent. Proceeding as described in ceeding as described in Example 1 once again a clean Example 3, with appropriate balancing once again the positive image is obtained of the wedge used as the positive-grey image of the original used, cleanly original. bleached on white at the corresponding points is ob- EXAMPLE 3 tamed A photographic material with three colour layers EXAMPLE 5 contains on a white-opaque cellulose acetate film a red- A photographic material as described in Example 3 sensitive silver bromide emulsion with the blue-green is as stated exposedinto the three spectral areas. Subse- .dye of formula quently the copy is developed as follows:

0"CH Q-co-xm OH 3 OH N=N N=N (102) H H C0 9 3 s0 thereover an empty gelatin separating layer and then a 1. develop for 7 minutes in a bath containing per litre green-sensitive silver bromide emulsion with the purple g of anhydrous sodium sulphite, 0.2g of l-phedye of formula nyl-3-pyrazolidone, 6g of hydroquinone, 35g of an- (103) NH H N N=N I 111 1-0 .m-can-Q-c O-HI-IQ-EEN 0H ll H H0 8 I O H0 8 H0 S H0 5 V i 3 After a further separating layer follows a layer with a hydrous sodium carbonate, 4g of potassium broyellow filter dye or colloidal silver acting as a yellow filmide, 0.3g of benzotriazole and 20ml of a 4.10 ter, over which there is a silver bromide layer with the molar solution of compound C in acetone; yellow dye of formula 2. fix for 2 minutes with a solution of 20g of sodium S0 H H0 S 0-CH H C-O N=N NH-COQ-CO-EEIQEEN 4) HO S 3 3 thiosulphate, 10g of anhydrous sodium sulphite and 10ml of glacial acetic acid per litre;

3. rinse for 2 minutes;

4. colour-bleach for 10 minutes with a solution of 10g of potassium iodide in 1 litre of sulphuric acid;

5. rinse for 2 minutes;

6. bleach the remaining silver for 8 minutes with a bath containing per litre 150ml of 37 percent hydrochloric acid, 25g of copper sulphate and 30g of potassium bromide; 7. rinse for 2 minutes; 8. fix for 3 minutes, as under 2); 9. rinse for 10 minutes. After drying a neutral wedge is obtained with a clean white and clearly graduated gradation.

EXAMPLE 6 On a 13 X 18cm glass plate is cast a solution with the methylaminophenolsulphate, 4g of hydroquinone,-

lOg of anhydrous sodium carbonate, 2g of potassium bromide and 3g of sodium thiocyanate;

2. rinse for 2 minutes;

3. oxidise for 2 minutes with a solution of 5g of potassium bichromate and 5ml of 96 percent sulphuric acid per litre of solution;

4. rinse for 4 minutes;

5. rinse for 5 minutes with a solution of 50g of anhydrous sodium sulphite per litre;

6. rinse for 3 minutes;

7. develop for 4 minutes with a solution consisting of 2g of Calgon, 50g of anhydrous sodium sulphite,

g of hydroquinone, 50g of anhydrous sodium carbonate, 2g of l-phenyl-3-pyrazolidone and ml of a l percent t-butyl-aminoborane solutin per litre;

8. rinse for 2 minutes;

9. colour bleach for 6 minutes with a colour bleaching bath containing per litre 27ml of 96 percent sulphuric acid, 10g of potassium iodide and 10ml of a 4.10 molar solution of compound D in ethanol;

10. rinse for 2 minutes;

1 1. bleach for 2 minutes of the residual silver as described in Example 1 under 6);

12. rinse for 2 minutes;

13. fix for 4 minutes as described in Example I under l4. rinse for 10 minutes;

After drying a clear, bleached colourless image of the wedge used with opposite gradation is obtained.

Instead of compound D it is possible to use compound C or another quinoxaline described in the table in a suitable photographically inactive, water-miscible solvent. Proceeding as described in this Example, once again a clean bleached colourless image of the exposed wedge with opposite gradation is obtained.

EXAMPLE 7 3.3ml of a silver bromide solution containing 5.3g of silver per 100g of emulsion, 1.0m] of a 1 percent solution of the hardener described in Example 1, 0.3ml of a 1 percent solution of the blue-green dye of formula (101) described in Example I, 0.5ml of a 4.10 molar solution of compound G in acetone and 1.6m] of water is caston a 13 X 18cm glass plate. After drying on the thus obtained layer a step wedge is copied lux, 10 sec.) and the copy processed further as described in Example 1. After drying a clean bleached colourless positive image is obtained of the wedge used as the original.

EXAMPLE 8 A photographic material as described in Example 3 is, as described in Example 3, exposed into the three spectral areas. The copy is then treated as follows:

1. develop 7 minutes in a bath containing per litre' 20g of anhydrous sodium sulphite, 10g of anhydrous sodium carbonate, 4g of hydroquinone, lg of 4-methylaininophenol-sulphate, 2g of potassium bromide and 10ml of a 4.10" molar solution of compound G in acetone;

2. fix for 2 minutes with a solution of 200g of sodium thiosulphate, 15g of anhydrous sodium sulphite, 25g 'of crystallised sodium acetate and 13ml of glacial acetic acid per litre;

3. rinse for 2 minutes;

4. colour bleach for 10 minutes with a solution containing 10g of potassium iodide, 27ml of 96 percent sulphuric acid and 5ml of a 4.10 molar solution of compound G in acetone per litre;

5. rinse for 2 minutes;

6. bleach the remaining silver for 8 minutes, as described in Example 5 under 6);

7. rinse for 2 minutes;

8. fix for 3 minutes as under 2);

9. rinse for 10 minutes.

'After drying a clean, white bleached positive image of the original is obtained.

EXAMPLE 9 On a 13 X 18cm glass plate is cast a solution of 3.3ml of 6 percent gelatin, 2.0ml of a 1 percent solution of the hardener described in Example 1, 3.3ml of a silver bromide emulsion containing per 100g of emulsion, 5.3g

of silver, 0.3ml of a 1 percent solution of the blue-green dye of formula l0 1) and l lml of water. After drying, a step wedge is copied thereon (50lux, 3 sec.) and the copy is treated as follows:

develop for 6 minutes;

fix for 2 minutes;

rinse for 4 minutes as described in Example 1;

colour bleach for 6 minutes with a solution containing per litre 27ml of 96percent sulphuric acid, 10g of potassium iodide and 10ml of a 4.107 molar solution of one of the compounds Her I in dimethyl formamide.

After rinsing for 2 minutes the remaining silver is oxidised as described in Example 1 under 6), rinsed and fixed as described hereinbefore. The copy is thoroughly washed and dried. In all cases, a clean bleached colourless blue-green wedge is obtained, whose gradation is parallel to the original.

EXAMPLE 10 ml of a 1 percent solution of the hardener described in Example 1, 3.3m] of a silver bromide emulsion containing 5.3g of silver per 100g of emulsion and 0.4m]

of water is cast on a 13 X 18cm glass plate. After drying a step wedge is copied thereon (50 lux, 5 sec.) and the copy is treated as follows:

Develop and fix as described in Example 1, colour bleach for 6 minutes with a solution containing per litre 10g of potassium iodide, 27ml of 96 percent sulphuric acid and 10ml of a 4.10 molar solution of compound A, B, C or H in ethanol or in another suitable watermiscible, photographically inactive solvent. After briefly rinsing, the remaining silver is oxidised as described hereinbefore, rinsed and fixed. After thorough washing-out and drying in all cases a clean bleached colourless image of the original used is obtained with a clearly graduated gradation.

EXAMPLE I l A 13 X 18cm glass plate is coated with a solution of 3.3m] of 6 percent solution of the hardener described in Example 1, 3.3m] of a silver bromide emulsion containing 5.3g of silver per 100g of emulsion, 0.5m] of the yellow dye of formula and 0.9ml of water. After drying a step wedge is copied thereon (50 lux, 5 sec.) and treated analogously to Examples 9 and 10, whereby instead of the compoundscontained therein the colour bleaching bath contains 10ml of 4.10 molar solution of one of the substances B, F and J in acetone or another suitable, watermiscible photographically inactive solvent. After drying a clean bleached colourless yellow image of the original used is obtained.

EXAMPLE 12 On a photographic material as described in Example 10 a step wedge is exposed (500 lux, 10 sec). The strip described in Examples 5 and 6, then rinsing, fixing and -co-Q rinsing again a purple wedge is obtained having an opposite gradation to the original.

We claim:

1. A quinoxaline of the formula 2. A quinoxaline according to claim 1, of the formula 40 wherein A and A are each alkyl with maximum 3 carbon atoms or pherlyl and n is l or 2.

3. A, quinoxaline according to claim 1, of the formula sol wherein A and A are each a methyl or phenyl group and n is l or 2.

4. Quinoxalin'e according to claim 1 of the formula wherein A is a methyl or phenyl group and n is l or 2. 

1. A QUINOXALINE OF THE FORMULA
 2. A quinoxaline according to claim 1, of the formula
 3. A quinoxaline according to claim 1, of the formula
 4. Quinoxaline according to claim 1 of the formula 